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Diseases of Aquatic Organisms

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DAO 76:131-140 (2007)  -  doi:10.3354/dao076131

Histopathology of experimental scuticociliatosis in turbot Scophthalmus maximus

L. Puig1,*, R. Traveset2, O. Palenzuela3, F. Padrós1,2

1Departament de Biologia Animal, de Biologia Vegetal i d’Ecologia, Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain
22XRDA (Generalitat de Catalunya), Departament de Biologia Animal, de Biologia Vegetal i d’Ecologia, Facultat de Veterinària,Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Barcelona 08193, Spain
3Instituto de Acuicultura de Torre la Sal, Consejo Superior de Investigaciones Científicas, Ribera de Cabanes, Castellón, Spain

ABSTRACT: A scuticociliate strain (B-2), originally isolated from an outbreak in a turbot Scophthalmus maximus (= Psetta maxima) farm in Galicia (northwestern Spain) and maintained in axenic culture, was injected intracoelomically (lethal dose 80 equivalent, LD80) in healthy turbot (50 g). Ciliate-injected fish were kept under controlled conditions in a recirculating seawater system and sampled on Days 1 through 8, 10, 12 and 14 postinfection (PI). Necropsies were conducted and included blood collection from the caudal vein and samples of liver, spleen, heart, digestive tract, kidney, gills, abdominal wall and neurocranium taken for routine histology. Mortality occurred from Day 6 until Day 12 PI and reached 66.7% by the end of the experiment. Presence of ciliates in the coelomic fluid was scarce until Day 4 PI. Parasitaemia was only observed from Day 5 until Day 10 PI and its incidence was always low. Presence of scuticociliates in tissue sections followed a progressive pattern of diffusion, with ciliates showing preference for loose connective tissue and also a clear haematophagous activity. The most severely affected organs were the pancreas and digestive tract. No special tropism for nervous tissues was observed in this study. The inflammatory reaction was variable depending on the tissue. After 3 wk, survivors had apparently managed to extinguish the infection.

KEY WORDS: Scophthalmus maximus · Psetta maxima · Turbot · Histophagous ciliates · Experimental infection · Pathogenesis

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